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This has now changed with users such as provisioning > memory through CXL Dynamic Capacity Devices. Except the kernel does not support CXL Dynamic Capacity yet. > Lets instead use clflushopt and only invalidate the range in question. > The performance of course scales poorly with the region size but is > ultimately less invasive. > > Signed-off-by: Davidlohr Bueso > --- > arch/x86/mm/pat/set_memory.c | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c > index 6c6eb486f7a6..4a1c4f6bec17 100644 > --- a/arch/x86/mm/pat/set_memory.c > +++ b/arch/x86/mm/pat/set_memory.c > @@ -372,6 +372,19 @@ int cpu_cache_invalidate_memregion(phys_addr_t start, size_t len) > { > if (WARN_ON_ONCE(!cpu_cache_has_invalidate_memregion())) > return -ENXIO; > + > + if (static_cpu_has(X86_FEATURE_CLFLUSHOPT)) { > + void *vaddr = memremap(start, len, MEMREMAP_WB); How much of the cost is in the mapping management? I was not expecting that virtual address based flushing would be reasonable to call from all the places where cpu_cache_invalidate_memregion() is called to do physical flushing. If the concern is increased frequency of flushing due to dynamic capacity, and that dynamic capacity updates have a chance to be finer grained, then I would then expect some kind of tie into memory hotplug that can invalidate cache using the direct map.